1. Field of the Invention
The present invention relates to an apparatus for directly driving alight emitting diode (LED) with alternating current (AC) power.
2. Description of the Related Art
A Light Emitting Diode (LED) is a semiconductor device having a p-n junction structure and emitting light through the recombination of electrons and holes, and has recently been applied to various technological fields in accordance with the development of semiconductor technologies. In particular, LEDs have high efficiency, relatively long service lives, and environmentally friendly characteristics, as compared to existing incandescent light bulbs, and therefore applications thereof have been continuously broadened.
In general, LEDs may be driven by applying several volts of direct current (DC) power thereto, due to structures thereof, and therefore a separate unit is required in order to drive an LED with commercially available alternating current (AC) power which is generally used in domestically, commercially, industrially, and the like. In order to drive an LED with commercially available AC power, an apparatus for driving an LED includes a rectifier circuit, an AC-DC converter, and the like.
However, a general AC-DC converter has a large volume and high power consumption, and therefore, when the general AC-DC converter is applied to the apparatus for driving an LED, LED advantages such as high efficiency, a small packaging size, a long service life, and the like may be offset thereby.
Therefore, in recent years, research into an apparatus for directly driving an LED with AC power without any AC-DC converter has been conducted.
In a case in which an LED is directly driven by AC power without an AC-DC converter, a method of enabling a current to flow at a constant rate in such a manner that a plurality of LEDs may be respectively connected to a plurality of switches, and ON/OFF switching of the plurality of switches may be controlled in accordance with levels of the AC power may be generally used.
In the Related Art Document below, Patent Document 1 discloses an apparatus for driving an LED. Here, the apparatus may emit light directly from an LED with AC power by controlling operations of switches connected to middle and final nodes of an LED array. In Patent Document 2, there is disclosed an apparatus for driving an LED. Here, the apparatus may control ON/OFF switching of switches in an order in which an LED array is connected to the switches.
However, in both Patent Documents 1 and 2, technology for controlling the operation of the switch in accordance with levels of AC power has been described, but there is a problem in that electro-magnetic interference (EMI) may occur due to the switching operation. As a result, in order to solve this problem, a separate EMI filter may be adopted, resulting in increases in manufacturing costs and in a circuit area.